1. Technical Field
The present invention is related to a control apparatus which controls driving operations of a fuel pump to be mounted on a vehicle.
2. Background Art
While motors for driving fuel pumps to be mounted on vehicles are connected via electronic switches to batteries, the electronic switches are driven based upon a PWM signal having a predetermined frequency and a predetermined duty ratio, so that electric power is supplied to the motors in PWM control modes so as to be rotated.
Further, in a case that foreign articles such as dust are mixed into fuel, there are some possibilities that the mixed foreign articles may be meshed with vanes of the fuel pumps, and pipes of the fuel pumps may be clogged with the foreign articles. In such a case, the motors of the fuel pumps are locked, and thus, locking currents continuously flow through the motors. As a result, various sorts of electronic components such as the motors, wiring lines, and switches must be designed with employment of such an assumption that the above-described locking currents may continuously flow through these electronic components. In other words, diameters of the wiring lines and heat resisting temperatures of the switches must be determined, so that these electronic components are not electrically damaged even when such locking currents continuously flow through these electronic components. In addition, heat radiating constructions for radiating heat are required, while the heat is generated because the locking currents flow through these electronic components, which may conduct the below-mentioned drawbacks: That is, large-scaled circuits are necessarily required, and manufacturing cost is increased (see JP-A-2000-240522, for example).
In the fuel pump control apparatuses, when the motors for driving the fuel pumps are locked, the locking currents continuously flow through the motors. As a result, the above-mentioned fuel pump control apparatuses have such a problem that the electronic component must be designed in order that these electronic components can endure the above-described locking currents, and also, the heat radiating constructions are necessarily required.
The present invention has been made to solve the above-described problems of the above technique, and therefore, has an object to provide such a fuel pump control apparatus. That is, when a locking current flows through a motor for driving a fuel pump, the fuel pump control apparatus is capable of suppressing heat which is generated in connection with the locking current, and eventually, capable of making a circuit scale thereof compact.